1. Field of the Invention
The present invention generally relates to optical, gel-based devices that utilize the diffraction properties of crystalline colloidal arrays. More specifically, the present invention relates to polymerized crystalline colloidal array detectors whose diffraction wavelengths change in response to a variety of specific stimuli. These detectors have application in numerous chemical, environmental and medical technologies.
2. Background Art
Charged colloidal particles, when suspended in water, form a stable, crystalline dispersion due to interparticle coulomb repulsion forces. The property of structural ordering in such dispersions has been exploited in making devices such as narrow band optical rejection filters. The ordering phenomena in such colloidal suspensions have been useful in spectroscopy and Bragg diffraction techniques. It has been found that mesoscopic, crystalline structures can have many practical applications as optical filters in military, space, medical and research uses. In many such instances, it is necessary or desirable to filter narrow bands of selected wavelengths from a broader spectrum of incident radiation. Crystalline structures, or crystalline colloidal arrays (CCA), and their use in optical filtering devices are disclosed, for example, in U.S. Pat. Nos. 4,627,689 and 4,632,517.
Similar devices, in which a CCA is embedded in a polymer matrix, have also been disclosed. For example, U.S. Patent Nos. 5,368,781 and 5,266,238 disclose tunable, narrow band radiation filters comprising a crystalline colloidal array of charged particles fixed in a hydrogel film. Methods for filtering incident radiation using these filters are also disclosed.
U.S. Pat. Nos. 5,330,685, 5,338,492 and 5,342,552 discuss narrow band radiation filters comprising a CCA of charged particles in a polymeric hydrogel. U.S. Pat. No. 5,281,370 also discloses a method of making a solid radiation filter material including one embodiment in which the particles in the array are fused together by polymerization.
Various sensor devices are also reported in the art. Schalkhammer, et al., disclose an optical sensor that utilizes the concept of pH-dependent swelling of special polymers. See Schalkhammer, et al., xe2x80x9cThe Use of Metal-island-coated pH Sensitive Swelling Polymers for Biosensor Applicationsxe2x80x9d, Sensors and Actuators B, Vol. 24-25, pp. 166-172 (1995). Conductimetric sensor devices have been proposed based on the selective swelling of hydrogels in response to pH by Sheppard, xe2x80x9cDesign of a Conductimetric Microsensor Based on Reversibly Swelling Polymer Hydrogelsxe2x80x9d, Transducers ""91, 773-776 (1991) and Sheppard, et al., xe2x80x9cMicrofabricated Conductimetric pH Sensorxe2x80x9d, Sensors and Actuators B, Vol. 28, pp. 95-102 (1995). Finally, sensor devices based on the selective swelling of hydrogels in response to glucose have been proposed by McCurley, xe2x80x9cAn Optical Biosensor Using A Fluorescent, Swelling Sensing Elementxe2x80x9d, Biosensors and Bioelectronics, Vol. 9, pp. 527-533 (1994) and Kikuchi, et al., xe2x80x9cGlucose-Sensing Electrode Coated With Polymer Complex Gel Containing Phenylboronic Acidxe2x80x9d, Anal. Chem., Vol. 68, pp. 823-828 (1996).
None of the art, however, discloses a sensor device that utilizes crystalline colloidal array diffraction as a detection means, as disclosed herein.
The present invention is generally directed to devices comprising a hydrogel that undergoes a volume change in response to a specific chemical species, and a crystalline colloidal array (CCA) polymerized within said hydrogel. Because the volume of the hydrogel changes, the lattice spacing of the CCA embedded therein changes as well. The light diffraction properties of the CCA change as the lattice spacing is changed. Measuring the change in diffraction, therefore, indicates the presence or absence of the stimuli that causes the volume of the hydrogel to change. The present invention is also directed to methods for making and using these devices.
The devices of the present invention can be used to detect a number of specific stimuli. For example, they can be used to detect the presence of various chemicals, such as metal ions in solution and organic molecules such as glucose, making the devices useful for chemical analysis. The devices can also be used to detect the presence of various gasses in solution. As a biomedical detection device, these sensors can be used to detect the presence of antigens from various sources, antibodies from various sources, and viruses such as HIV. These devices can be further used as xe2x80x9csense and dispensexe2x80x9d mechanisms which detect the presence of a particular stimulus and, in response to that stimulus, release a drug or other therapeutic agent. Since none of these devices is incompatible with living cells, their use both in vitro and in vivo is contemplated. One skilled in the art will appreciate that the various embodiments disclosed herein, as well as other embodiments within the scope of the invention, will have numerous applications in the environmental, medical, pharmaceutical, metallurgy and chemical fields.
It is an object of the present invention to provide a sensor device comprising a CCA polymerized in a hydrogel that changes volume in response to stimuli.
It is a further object of the invention to provide a sensor device that utilizes the light diffraction properties of a CCA to detect the presence of various stimuli.
A further object of the present invention is to provide a sensor device that swells in response to various stimuli, thereby changing the diffraction properties of the sensor.
Another object of the invention is to provide a sensor device for detecting the presence of chemicals.
Another object of the invention is to provide a sensor device for detecting the presence of gasses in solution.
Another object of the invention is to provide a sensor device for detecting the presence of various medical conditions.
Another object of the invention is to provide a sensor device for detecting the presence of biological molecules.
It is another object of the present invention is to provide a sensor device useful in environmental applications.
Another object of the present invention is to provide a sensor device having application in the field of medical diagnostics.
A further object of the present invention is to provide a sensor device useful for dispensing therapeutic agents in vivo in response to the presence of stimuli.
These and other objects of the invention will be more fully understood from the following description of the invention.